Name:	rdn_DefinedContributionPlanEmployeeDiscretionaryContributionMaximumAmount
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the period over which an employee is required to provide service before the company will make discretionary, pro rata (based on eligible pay) cash allocations to each eligible participant’s account, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	rdn_DefinedContributionPlanEmployerMatchingContributionArrangementwithIndividualRequisiteServicePeriod
Namespace Prefix:	rdn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of years in which the entity provided certain participants who were active in our pension plan with yearly cash "transition credits" if employed by the entity during this time.

No definition available.

Name:	rdn_DefinedContributionPlansNumberofYearstoApplyTransitionCreditsforActivePensionPlanParticipants
Namespace Prefix:	rdn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

Name:	us-gaap_CashSurrenderValueOfLifeInsurance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of the cost recognized during the period for defined contribution plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DefinedContributionPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Maximum amount the employee may contribute to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

No definition available.